When Ehcache is running in the EJB Container, for example for Hibernate caching, it is in technical breach of the EJB rules. Some app servers let you override this restriction. I am not exactly sure how this in done in Glassfish. For a number of reasons we run Glassfish without the Security Manager, and we do not have any issues. In domain.xml ensure that the following is not included.

Ehcache page caching versions below Ehcache 1.3 get an IllegalStateException in Glassfish. This issue was fixed in Ehcache 1.3.

This exception is thrown when using Ehcache with my Glassfish cluster, but Ehcache and Glassfish clustering have nothing to do with each other. The error is caused because Ehcache has received a multicast message from the Glassfish cluster. Ensure that Ehcache clustering has its own unique multicast address (different from Glassfish).